1. Field of the Invention
This invention relates to certain novel blends of phenolic cyanate-phenolic triazine copolymers and epoxy resins, as well as to articles prepared from said blends. More particularly, this invention relates to such blends which have improved properties.
2. Prior Art
Phenolic resins are a class of synthetic materials which greatly vary in molecular structure. Therefore, a multitude of applications for these products exists as a result of the array of physical properties that arise from the synthetic options. However, phenolics disadvantageously exhibit less than desirable thermal oxidative stability and produce an extensive, uncontrollable amount of volatile by-products during crosslinking.
In order to obviate certain of the disadvantages attendant to phenolics, U.S. Pat. No. 4,970,276 proposed a modified multifunctional phenolic cyanate/phenolic triazine copolymer ("PT resin") which had greater oxidative, mechanical, and thermal stability as compared to conventional phenolic resins, and did not produce volatile by-products during crosslinking. Further, these PT resins possessed better elongation properties and higher glass transition temperatures than the conventional phenolic resins. Additional examples of such PT resins are described in U.S. Pat. Nos. 4,970,276, 4,978,727, and 5,126,412.
Another approach for producing thermosettable blends having improved mechanical properties is by blending dicyanate esters with epoxy resins as disclosed in U.S. Pat. Nos. 4,612,359, 4,506,603, 4,477,629, 4,546,131, 4,487,915, 3,562,214 and in Shimp, et al., "Co-Reaction of Epoxide and Cyanate Resins," 33rd Int'l SAMPE Symposium and Exhibition 1-13 (Calif. Mar. 7-10, 1988) and Shimp, AroCy.RTM. Cyanate Ester Resins Chemistry, Properties & Applications, (3rd Ed. May, 1991). These blends have been useful in the production of base materials for printed circuits as disclosed in U.S. Pat. Nos. DE 4,022,255, DD 290,844, DE 4,125,420, and DE 4,224,835.
Although the above inventions provide thermosettable resin blends which, when cured, possess excellent thermal stability and mechanical properties, there is room for additional improvement in the overall mechanical properties, especially in glass transition temperature, as well as in water absorption.
It would be desirable to provide a thermosettable resin blend which, when cured, is superior to prior art phenolic resins and dicyanate blends in one or more of the properties selected from glass transition temperature, flexural strength, flexural modulus, elongation, and water absorption.